Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$198.65	5.441%	$209.4585	$209.46	$209.45	$209.50
Purchase #2	$81.37	6.338%	$86.5272	$86.53	$86.55	$86.50
Purchase #3	$128.37	12.728%	$144.7089	$144.71	$144.70	$144.70
Purchase #4	$223.76	7.647%	$240.8709	$240.87	$240.85	$240.90
Purchase #5	$199.73	4.674%	$209.0654	$209.07	$209.05	$209.10
Purchase #6	$128.50	13.506%	$145.8552	$145.86	$145.85	$145.90
Purchase #7	$129.87	12.438%	$146.0232	$146.02	$146.00	$146.00
7 purchase totals =	$1,090.25		$1,182.5093	$1,182.52	$1,182.45	$1,182.60